1. Field of the Invention
This invention relates to data processing systems. More particularly, this invention relates to data processing systems having a plurality of registers for storing data words to be manipulated by an arithmetic logic unit operating under control of program instruction words.
2. Description of the Prior Art
It is known to provide program instructions that specify whether an operation is to be performed on input operands contained in one register or an input operand contained in two registers but treated as a single input operand.